This invention relates to an improved tire valve assembly which provides improved corrosion resistance both to the valve body and to the valve core assembly. The advantages of this invention are particularly important when the valve is used with a tire that is weighted with water containing a dissolved salt.
It is common practice to weight the tires of many agricultural and heavy construction vehicles by partially filling the tire with water. In order to lower the freezing point of the water, salts such as sodium chloride or calcium chloride are typically dissolved in the water.
Tire valves used in such applications must meet a number of demanding requirements. In particular, such valves are subject to the highly corrosive environment of a salt solution. In addition, when water is being introduced into the tire it is important that the valve provide a high volume, low resistance path.
In the past, a number of different approaches have been used in an attempt to minimize corrosion of such valves. Stasiunas U.S. Pat. No. 4,404,985, assigned to the assignee of the present invention, discloses an air-liquid valve for off-the-road vehicle tires which embeds the lower end of the valve body in an elastomeric base member. Though the Stasiunas valve provides important improvements over conventional valves, it still allows salt solutions to come into contact with the zone of bonding between the elastomeric base member and the brass valve body. Salt solutions can cause corrosion of the brass valve body and de-bonding of the elastomeric base member from the valve body.
Iknayan Canadian Pat. No. 556,936 suggests another approach to protecting a valve body from corrosion. In the Iknayan valve a collar of a metal more anodic than the brass valve body is placed at the end of the valve body. Iknayan teaches that in the event that the bond between the rubber and the brass insert becomes exposed to the influence of any corroding material within the inner tube (such as water or a salt solution) the bond between the rubber and the brass insert is protected by the presence of the metal more anodic than the brass insert.
Boyer U.S. Pat. No. 2,778,374 discloses a third approach. In Boyer, a flanged ring is pressed onto the valve body from below in order to make a seal between the ring and the valve body and to capture the elastomeric base member in place. Boyer relies on the seal between the valve body and the flanged ring to eliminate leakage of air or liquid which might destroy the bond between the valve body and the base member.
It is an object of the present invention to provide an improved tire valve assembly which isolates the entire valve body from any liquid contained in the tire and which additionally provides improved protection to the interior of the valve core housing.